In fresh-water drowning, the sequence of haematological changes differs from salt-water drowning because:

• A Fresh water is absorbed across the alveoli into blood, causing haemodilution, haemolysis, and hyperkalaemia ✓
• B Fresh water is hypertonic, drawing water from RBCs causing haemoconcentration and hyperkalaemia
• C Salt water is isotonic; no haematological change occurs in salt-water drowning
• D Both fresh and salt water cause identical haematological changes regardless of osmolarity

Explanation

Fresh water is hypotonic relative to blood; it is rapidly absorbed across the thin alveolar membrane into the circulation, causing haemodilution (↓plasma osmolality, ↓sodium), haemolysis (hypotonic lysis of RBCs releasing K⁺), hyperkalaemia, and ventricular fibrillation. In salt-water (hypertonic) drowning, water shifts from blood into alveoli, causing haemoconcentration, pulmonary oedema, and hypernatraemia — death occurs from asphyxia and pulmonary oedema rather than cardiac arrhythmia.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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